Botswana-based NGO Raptors Botswana recently fitted 14 vultures of four different species with satellite tracking devices to enable their daily movements to be monitored.

“In order to conserve our vultures, which are globally threatened, we need to know where they are breeding and feeding, and what threats they faceon a daily basis,” said researcher Dr Glyn Maude.

Raptors Botswana obtained a substantial grant from the Denver Zoological Foundation Conservation Division to purchase and fit a sample of vultures with the latest solar-powered transmitters. The transmitters are no bigger than a cellphone, in most cases weigh less than 1% of the bird’s body mass, and are attached by means of a back-pack harness. But how do you catch a vulture in order to fit the transmitter?

“After experimenting with a variety of techniques, we settled for a compressed-air powered cannon net machine,” said Maude. The remotely triggered device fired a net over feeding vultures.

Once the vultures were netted, the research team, under the guidance of PhD student Rebecca Garbett, measured and weighed each bird, ringed it with an aluminium leg band, fitted a pair of uniquely numbered wing tags and then fastened the transmitter before releasing the bird – all in less than 30 minutes.

The transmitter sendssatellite signals every two hours. “Contrary to our expectations, based on a literature survey, we have found that the lappet-faced vultures are inveterate travellers,” said Garbett. “It was thought that they had small home ranges, but this couldn’t be farther from the truth.”

Birds from the Central Kalahari Game Reserve fly regularly into Namibia and South Africa, covering distances of up to 800km, spend a few days in the new location, and then fly back along a dead-straight flight-path to their point of departure.

“It is not clear why lappet-faced vultures make these long range forays,” said Garbett, “but one thing is clear, these birds are vulnerable to poisoning and other threats anywhere in the southern African region.”

There have been numerous incidents of large numbers of vultures being poisoned in Botswana, Namibia, South Africa and Zimbabwe over the past few years. In some cases, vultures are the innocent victims of poison put out for ‘problem’ predators, but there is a growing number of cases where poachers have laced elephant and giraffe carcases with poison specifically to eliminate vultures which alert and lead anti-poaching forces to the scene of the crime.

White-backed and hooded vultures have also been shown to undertake extensive trans-boundary movements. This is of special concern since thesespecies are now classified as globally ‘Endangered’ due to precipitous declines in their populations throughout Africa.

Hooded vultures which were fitted with transmitters in the Okavango Delta moved north into Chobe National Park and southern Angola, and subsequently returned to their capture sites.

White-headed vultures, by contrast, have been found to be more sedentary. According to Garbett, a pair of white-headed vultures has remained within the protected confines of the Central Kalahari Game Reserve for the past year.

“It is almost as though they know where the park boundaries are, because although they traverse the whole park, they seldom venture beyond its limits”, Garbett reported. This is good news for this species, considered globally ‘Vulnerable’ - but not always: recently two were poisoned at Pandamatenga, adjacent to the Chobe National Park.

The research highlightsthe vulnerability of vulture populations to human-induced threats; it also clearly establishes the regional nature of the problem. Space age technology has helped unravel some of the issues facing vultures today – will it help ensure their survival?